text:
Can you accept a LAHSO on your private pilot checkride?
Suppose you're on your private pilot checkride and the tower gives you a land and hold short clearance.
Are you able to accept that clearance? I know you're expected to fly as if you were a private pilot, and you're allowed to carry the examiner even though they're not providing you dual instruction...
Are you allowed to accept a clearance on your private pilot checkride that you couldn't accept as a student but could as a private pilot?

I would suggest editing your question to either ask specifically about LAHSO (like your title) or ask the more general question (like the bolded last sentence of your question) because the answer might not be the same!

What clearance, besides a LAHSO, can a private pilot accept that a student cannot?

@jun Flight into class B, perhaps.

@SteveV. Students can fly into class B with the proper endorsement, and it's common to get one if you train under/near such.  I had one, and I actually flew in the local class B on my PPL checkride.

First, let's see whether it's legal. FAA Order 7110.118 notes that:

7. EXPLANATION OF CHANGES.
The following changes apply to all LAHSO.

a. ...
b. Solo student pilots will not conduct LAHSO.

However, you could interpret that as not applicable to your situation, as you are not the sole occupant of the aircraft:

14 CFR §61.87
(a) General. ... The term "solo flight" as used in this subpart means that flight time during which a student pilot is the sole occupant of the aircraft...

Though it might be allowed, note it does not say must:

AIM 4-3-11(b)

...
Student pilots or pilots not familiar with LAHSO should not participate in the program.

I'd recommend against doing so because LAHSO can add to your workload, especially if you're a bit nervous on your checkride. Also, the AIM note on discouraging LAHSO is rather valid and if done improperly, can affect safety. Having said that, the examiner is likely to ask questions on LAHSO during your practical examination, especially since LAHSO is a special emphasis area in the PTS. This may include:

Requirements to accept a LAHSO clearance
ATC pharseology for LAHSO
Pilot responsibilities while carrying out LAHSO

In any case, always remember that you do not need to accept a LAHSO clearance -- if you do not feel comfortable with doing so, ATC will provide arrangements to land full-length on the same runway or another one. You should not accept a LAHSO clearance if you believe doing so would compromise safety.

Note: this does not necessarily apply to all situations where a student pilot is prohibited from doing something that a private pilot would be able to do.

Everything that you quoted seems pretty clear that it would be permitted.  Note however that the bolded part of his question is more generic than just LAHSO, and asks about the general case.

@Lnafziger: general case is less clear-cut, most likely since you aren't a private pilot yet and you're (usually) the PIC, then you wouldn't be able to do so.

I disagree with your comment, although I agree with your OP basically entirely. "The term solo flight as used in this subpart means that flight time during which a student pilot is the sole occupant of the aircraft" seems pretty clear-cut to me. Although the point you make about it being discouraged in the AIM is very valid. 61.47 Says that the examiner and anyone else he deems is not subject to the limitations of carriage of PAX but not that he is invisible or that it counts as a 'solo' flight.

From my checkride, I can say that the examiner strongly discouraged LAHSO operations in general.  That's not to say you can't do it perhaps, but you probably shouldn't do it (@Qantas 94 Heavy has a great analysis of the rules behind LAHSO, so no sense in repeating them).  Things to consider include making sure you have enough available landing distance and check against conditions with your aircraft performance data.  Remember, the examiner is testing, among other things, your decision making skills as a pilot.  Your examiner would probably be more impressed by declining a LAHSO clearance and landing safely with full-length than trying to show off to the examiner.  You already have to demonstrate a short and soft takeoff and landing -- probably not much sense in trying to go overboard.
Personally, as a recently-certificated pilot with only about 60 hours of experience, I'd still decline a LAHSO clearance if given one.  There's nothing that says you need to take one, especially if you feel it may compromise your safety.

I think your general characterization of a LAHSO might be a little bit extreme. If a quick mental assessment concludes it might require short-field operations, then I would be unlikely to accept, but I've seen operations where the hold short distance is 5000 feet, which is longer than many full-length runways I land on. Accepting a clearance like that is not "showing off" in my mind. Showing off is always the wrong reason to accept a clearance.

Oh, yes.  You're right that you should be able to do a quick mental calculation to determine if you can land safely, but therein lies the point (you should have the runway data handy and be confident in your skills).  I was also trying to emphasize some of the things my examiner in particular discussed (actually outright told me). His concern was more with knowing what it was and that you could decline it (basically said don't do it--there's no need, and why pressure yourself?).  The one field here near me actually discontinued LAHSO.

90% of land and hold short clearances that I've seen or taken part in have been at airports with two runways that intersect at the end. They take 500 feet off a 6,000 foot runway. If you decline one of those clearances out of principle, you're doing virtually nothing to increase safety and just wasting everyone's time. If you don't know the LAHSO distance, just ask. Any tower controller will have it memorized.

Strictly speaking you are technically flying as a private pilot and pilot in command on your check ride, you are not flying as a student pilot, the DPE doesn't even need to have a current medical certificate. It is a strange sounding thing but the check-flight is the one flight where you are not required to hold the certificate for that type of flight being conducted. The flight will be logged as a private pilot, it will not be logged as a student pilot.
To put it another way, you are essentially considered a qualified private pilot when your instructor endorses your for the check-ride. The check-ride is just a confirmation and it is as much about double checking your instructor's judgment as it is about your skills.
So yes, you can do anything a private pilot can do during your check ride. If you want a belt and suspenders answer then just ask the examiner during the question and answer portion before the exam officially starts, in the end it is their interpretation that counts.(unless they are way out of line and you need to appeal to the FAA) It will not count against you as it is something unique to the exam environment not to normal flying, and it is not a test item in the ACS.

This is absolutely false. You are not a private pilot when your instructor endorses you. The DPE will probably have a medical certificate. You do not log it "as a private pilot". You don't have the privileges of a PPL until the DPE signs at the end of your flight, until then, you are a student flying with a qualified instructor (the DPE). The DPE has authority to end the flight and take control if required.

You are not a private pilot until you are issued a certificate saying so. Otherwise, carrying a DPE would not be an explicit exception to the rule against student pilots carrying passengers.

A DPE is not an instructor and is not acting as an instructor in any capacity during a check flight. While it would be rare a DPE does not even need to be able to act as a pilot in command. The DPE is legally a passenger and the applicant is assuming all responsibilities of the private pilot certificate. I never said the endorsement awards privileges, I said you are considered qualified pending a final confirmation, comprehension of the detail is key.

@Ron I never said that you are a private pilot when an instructor endorses you, I said you have met all requirements of PP and the DPE is there to confirm this. The student is an acting private pilot during the check flight. You do log it as PIC, the DPE is acting as a passenger-observer not in anyway a flight instructor. The FAA explicitly and strongly discourages any instructor-like interactions during the exam.


text:
May an emergency aircraft land on a closed runway?
Let's say that you're on approach to a remote airport to refuel (for arguments sake, Funafuti International Airport, Tuvalu), with 1-2 hours of fuel remaining in your aircraft. Contacting ATC to request permission to land, they tell you that the only runway is closed for an unspecified reason and will not reopen for ~2 hours.
The nearest airport is 295nm away, so you agree to hold, hoping the runway is soon reopened. After waiting a little while, the runway is still not reopened, so you declare an emergency.
Is the airport required to reopen the runway? Does the fact that the nation is not a part of The Chicago Convention change anything?*
Supposing ATC refuse to reopen the runway, is the pilot permitted to land anyway?
Let's presume the aircraft is not certified for ditching.
Searching Google, I found that at least one emergency aircraft has landed on a closed runway.

* 2020 update: in Nov 2017 Tuvalu became ICAO's 192nd member state (icao.int).

With reference to your example, I'm pretty certain that an airliner can cover 295nm in less than an hour, even when respecting the <= 250 KIAS @ FL <=100 rule (which doesn't apply to emergency situations anyway).

@shortstheory Perhaps an airliner could, but I was referring to small planes.

You may have 1-2 hours of fuel on board but other things may require you to land asap. An engine fire for instance... or low oil pressure etc  . The airport on the other hand may have been closed for runway work and while they may realise you have no other choice other than clear all man and machine off the runway and pray for you. At the end you are in-charge of getting the airplane down with no loss of life.

In an emergency, use of a runway is optional.

Preflight Planning

Let's say that you're on approach to a remote airport to refuel, with
  1-2 hours of fuel remaining in your aircraft. ...
The nearest airport is 3-4 hours away...

First of all, it looks as if the pilot has already broken several regulations in order to end up in this situation.  He either didn't file an alternate, or if he did then he didn't carry enough fuel to get to it (and additional reserves as required).  If the runway is closed for an extended period of time, there would likely have been a NOTAM stating that the runway would be closed.  All of this sounds like poor preflight planning, and probably the 'ole careless and reckless thrown in for good measure.
The Problem

Contacting ATC to request permission to land, they tell you that the only runway is
  closed for an unspecified reason and will not reopen for ~2 hours.

Okay, we need to figure out what the "unspecified reason" is because this can change things dramatically.

Is it for endangered migrating turtles?

Is it for construction?
In any case, he needs to use all available resources.  Talk to ATC and explain the situation. Ask them how they can help clear the runway so that we can land.  He should tell them that an emergency is imminent without their assistance.  They will do everything that they can to help you, including coordinating with people on the ground to get out of the way.  Be creative.  Did you know that there is no regulation (in the US) requiring you to land on an actual runway?  Ask them if you can land on the taxiway.  For that matter, land in the grass beside the runway.  It would be better than going for a swim or crashing after running out of gas!

Let's presume the airport is surrounded by ocean, and the aircraft is not certified for ditching.

Ummm, who cares if it is certified for ditching?  If you are over water, it doesn't matter.  If you are over land, it doesn't matter.  If you have a choice, pick land (even if it's off-airport).

Supposing ATC refuse to reopen the runway, is the pilot permitted to land anyway?

Well, they wouldn't really do this unless there was a really good reason, mainly meaning that it would be dangerous for the aircraft to land there (like in the second picture above).  In this case, we can't really ignore ATC and land anyway until:
Declaring the Emergency

...so you choose to hold, hoping the runway is soon reopened. After
  waiting a while, the runway is still not reopened, so you declare an
  emergency.

At least our poor pilot did this right.  Rather than blindly continuing to hold, he declared an emergency.
Getting on the Ground
Now we have a lot more latitude and options, and ATC is better able to help us because they can pretty much do whatever it takes to save the aircraft.  This can change a "Sorry, there is nothing I can do." into a "Cleared to land any runway or taxiway." all on its own. They may throw in a "Landing at your own risk." if there are still hazards, but that's just to clear them of liability.  Even if they still refuse, you can simply advise them of what you will be doing and go ahead and do it.  Keep in mind however, that it may be better to scope out an off-airport landing site if the danger is so great that ATC won't allow you to land even under such dire circumstances.
Remember, the pilot is the final authority for safe operation of the aircraft.  Get on the ground and sort it out after the fact. (Poor turtles....)
In the end, just do what you can to stay alive, and preferably use the airplane again.  There are going to be tons of questions and probably major legal battles.  Someone will probably go after the pilot's certificate.  On the bright side, he will be around to actually see it happen though.

It's not a requirement to file an alternate unless the forecast weather at the destination is below 2000 ft ceiling and 3 mi visibility +/- 1 hr of the intended time of landing.

there are also places where there is no alternate possible for many aircraft types. Say you're on a ferry flight to some Pacific island in a Mooney or C172. You're going to have reserves to circle a while, but the nearest island can be the one you took off from 5-6 hours earlier.

@RobP Sure.  In the US. Under Part 91.  I don't think that there are any airports that meet the above conditions in the US though.   :-)

"First of all, it looks as if the pilot has already broken several regulations in order to end up in this situation. He either didn't file an alternate, or if he did then he didn't carry enough fuel to get to it (and additional reserves as required). "-- the information given in the question doesn't indicate that there was any requirement to file a flight plan at all.

@quietflyer Well, if his destination is Funafuti, then it is an international flight, and flight plans are indeed required. Even if it wasn't, it's still poor planning as the pilot didn't plan for contingencies. This in itself may break regulations such as the "careless and reckless" one here in the US. At any rate, I stated that it "looks as if" he broke several regulations, and didn't say that they did for sure. I try to provide info that people can learn from, and hopefully allow them to think about situations like this in a different way so that they never happen in the first place!

Allot of blame here.  Consider a situation where WX or traffic conditions caused a low fuel condition, and that condition was timely reported to ATC.  Then an accident occurs on a runway.  In this situation the airport is not controlled, and the airport personnel go to attend to the accident, and the NOTAM gets delayed. On final the pilot is advised over CTAF of the only runway being closed. WX and current fuel state make diversion risky, and pilot decides to land on taxiway, after verifying there is not men or equipment on the taxiway and advising the airport of intentions.

There is plenty of room between the request to land, and declaring an emergency to sort things out. After all, if the runway is closed, the tower isn't too busy. It would probably go something like this:

ATIS: Runway 12 is closed.
Pilot: Foobar approach, N12345.
Tower: N12345 go ahead.
Pilot: Foobar approach, we are having some technical difficulties, please advise, what is the nature of the closure of runway 12? N12345.
Tower: N12345 Threshold is being painted.
Pilot: Yeah, approach, we may have a faulty gauge, we are showing a faster fuel burn than expected, we'd like to get on the ground and take a closer look, we can land a little long.
Tower: Roger N12345, report runway in sight.
Pilot: Runway 12 in sight, N12345.
Tower: N12345 You are cleared to land runway 12.

The pilot is then obligated to buy a box of donuts for the tower, and thank the tower and the ground crew. He may get a warning, but equipment failures do happen, and they aren't always an emergency.
Everybody makes mistakes. Aviation is as much an art as a science. So while the rules are important, they are only religion to the lawyers, and only then after something goes horribly wrong. To the people who actually work in aviation, it is about safety, and professionalism, and being good at what you do. And that requires a certain amount of flexibility.

If you already declared an emergency all bets are off, and you must do whatever is required to save the vehicle. There can be no talk about being 'permitted' or even 'cleared' to land if an emergency has been declared.
ICAO Annex 2 2.3.1 Responsibility of pilot-in-command

The pilot-in-command of an aircraft shall, whether manipulating the
  controls or not, be responsible for the operation of the aircraft in
  accordance with the rules of the air, except that the pilot-in-command
  may depart from these rules in circumstances that render such
  departure absolutely necessary in the interests of safety.

Faced with bad weather, some icing, and an aircraft with a collapsed gear on the runway, I landed on the taxiway.
The matter was complicated in that ATC was unaware of the runway closure.  This was at night, in the winter, and the airport owner / manager fired up his equipment to light up the incident area, and did not file a NOTAM until after I was on the ground.  I found out when I was five miles out on the approach and made a call on the CTAF.  I asked if the taxiway was plowed and free of equipment and personnel and was told it was, and announced my intentions. The airport manager acknowledged on the CTAF.
The FAA FSDO Inspector arrived as I did. Before we left, he came over and talked with me, and I mentioned that ATC was unaware of the incident. Nothing was said adverse to landing on the taxiway.
From my perspective, that option had less risk then doing a missed, and getting back up into the ice. With a light load already on the plane, it would have been hard to get above the icing layer.

Well, the runway closure would be NOTAM'd. I have no idea what the deal is in other countries, but in the US, per 14 CFR Part 91.3 "any pilot may deviate from any rule in this part to the extent of the emergency" or something similar. I would guess it's the same deal in other places. And if ATC is aware of it OR it is for the safety of those on board the aircraft, the FAA will not mind.

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text:
Why does manifold pressure increase when you turn on carb heat?
So everyone knows that carb heat decreases engine performance. Yet when we check the heat during run-up, the manifold pressure increases.
Why is that? Shouldn't adding carb heat cause the intake air to become hotter and therefore thinner, and cause the manifold pressure to decrease?

Because manifold pressure sucks! Seriously though, the manifold pressure measures how much the engine is able to reduce the pressure between throttle and inlet valve by sucking air into the cylinder.
When you apply carb heat the air gets routed over a heat exchanger that uses some of the excess heat from the exhaust system to heat up the intake air, however the reason it becomes less dense, is because the pressure stays the same. If you look at the so called ideal gas law, you'll notice that pressure is a function of density and temperature, if you have a closed system, where the density can not change, increasing the temperature would indeed increase pressure. This is not a closed system however, so the pressure actually stays more or less the same and the density decreases, and it's not the reason for the manifold pressure increase.
The thinner air leaves the engine with less oxygen to burn and thus it produces less power, the RPM drops, causing the engine to "suck" less air into the cylinder, this gives the air more time to sneak passed the throttle, and the manifold pressure rises. For the same reason the manifold pressure rises (slightly) when you reduce the RPM for cruise. Any reduction in RPM, for whatever reason – engine damage for example – as long as the throttle doesn't move (or if you have carb ice, which has essentially the same effect as closing the throttle), your manifold pressure will actually rise. Remember, it seems counter-intuitive, but the engine is fighting a battle with the throttle, trying to keep the manifold pressure down by sucking the air out, while the throttle is trying to increase the pressure back to atmospheric by letting air in.
When the throttle is anything but wide open, the situation looks like this (image borrowed from the linked article)

(source: avweb.com)
It's related to the fact that the manifold pressure gauge, when the engine is stopped, will read ambient pressure, i.e. 29.92 inHg on a standard day at sea level, which is usually interpreted as "full throttle", it doesn't matter how the throttle is positioned. So it's not really showing how much fuel/air mix you're shoving into the engine. In fact, we're not shoving at all, the engine literally sucks it into the cylinder as the piston moves out of the way during the intake stroke. In this particular case with the engine off, it just means that enough air was able to sneak by the throttle and equalize the pressure. It is not flowing nearly fast enough to equalize the pressure as soon as the engine is running though.

@fooot I tried; is it easier to understand now?

I wonder if some of the difference might come from bypassing the air filter. At least in the Lycoming-engined Cessnas I've flown, carb heat uses an alternate air source that is unfiltered. Wouldn't removing the resistance of the filter increase manifold pressure a bit?

@FredLarson hard to tell, possibly. It might be offset by the path through the heat-exchanger offering more resistance. You are correct though, all carb heats I know uses an alternate source without a filter.

Isn't the throttle in that diagram more of a choke? It might have contributed to the confusion in this question.

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text:
Why was the rate of part 121 LPV equipage projected to be so low, and has that projection come true?
On page 10 of the FAA's 2016 PBN Navigation Strategy document, found here, the USA part 121 fleet is very thoroughly equipped with RNAV capability....except for LPV.

Similarly, the FAA predicted that by 2025 only 13 percent of the 121 fleet would be capable of shooting LPV approaches.

Given the ever-growing number of high-quality LPV approaches available in the USA, why did the FAA believe LPV equipage among the airlines would remain so low?
And, were they correct?

In Europe, Cat I ILS will be prohibited by 2030 and be replaced by RNP approaches to LPV minima (source). So I expect things to change more quickly during the second half of this decade.

@Bianfable - This is extremely interesting, thank you!

Short answer: Money.
Part 121 operators, i.e. airlines, are interested in profit and running an airline is a low margin business. Aircraft are very big capital expenses. They cost a lot every day in interest and depreciation whether they are flying or not. But they only generate revenue when they are flying, so airlines try real hard to maximize the days the aircraft is in service. About 20 years ago, an airline told us that taking a 737 out of service for one day cost them $65k in lost revenue. On top of that, crews have to be trained to fly LPV approaches. That adds training costs.
Adding LPV to an existing aircraft requires an STC. So modifying aircraft to add it takes time and money. And sometimes the time out of service costs more than the actual labor and material to do the mods. Before an airline will make the mods, they will do a benefit analysis to see how long it will take to earn back the cost of the mods.
The issue with something like LPV capability is that it is only beneficial to the airline is if they have to have it to provide service to the airport. If all the airports they fly to have ILS approaches (and almost all airports in the US with scheduled service have at least one ILS), adding LPV doesn't add any benefit, so adding it is a waste of money. If they want to add service to an airport that only has LPV, then it has value. The next question is; how many aircraft suitably equipped are needed and how many crews need training? In the end, it makes business sense or it doesn't.
I suspect that most of the aircraft that are or will be equipped in the future are coming equipped from the factory. The incremental cost is small in production. Then the impact is training and scheduling.

Add to all of that, most approaches that have LPV minima also have slightly higher LNAV/VNAV minima that are usable without all the added cost + downtime.  So the question becomes, is gaining that increment of capability (worse weather that you can land out of) worth the costs incurred.  Or, you tell the airport, if you want our service, just put in an ILS.


text:
What does I1001 mean in a METAR remarks?
Here is an actual METAR example:
KOMA 190352Z 36017G26KT 3SM -SN OVC012 M08/M11 A3014
RMK AO2 PK WND 36027/0302 FZDZE37SNB27 SLP220 P0000 I1001 T10831111 $

What does the I1001 mean? I have also seen I1000, I1002, I1003, and I1004.

Are you sure it's a capital i and not the digit 1?

Yes, it is capital "i". I copy and pasted the METAR. If you goggle I1001 you might get some METARs with it. https://www.google.com/search?q=metar+i1001

It indicates ice accretion (buildup). This seems to be very obscure, I finally found it in some NOAA release notes for ASOS software v3.07:

(S01126) ADD ICE ACCRETION REMARK TO METAR/SPECI REPORTS

Discussion: The amount of ice accreting on a flat surface (planar
  icing) as estimated by the data from the freezing rain sensor, will be
  included in the remarks section of the METAR / SPECI reports. The
  remark will have the format of “Ihnnn,” where “h” is the hourly time
  period, i.e., 1, 3 or 6 hours. The value “nnn” is the ice thickness
  accumulated to the nearest 0.01 inch.
Please Note: In situations when FZRASN is manually entered in the
  Present Weather field, an inappropriate trace accretion amount (I1000,
  I3000, I6000) might be entered in the remarks section of the METAR /
  SPECI reports. This is a known issue and will be addressed at a later
  time.

Based on that, "I1001" means ice buildup of 0.01 inches in the last 1 hour.
And thanks to Jimmy for finding a more official source: FCM-H1-2017, Federal Meteorological Handbook No. 1 - Surface Weather Observations and Reports (p. 12-18) from OFCM, the Office of the Federal Coordinator for Meteorology.

That is correct, but a better source would be the NOAA instruction manual for putting together METARs and other observations.  FCM-H1-2017, Para 12.7.2.i.  https://www.ofcm.gov/publications/fmh/FMH1/FMH1_2017.pdf
Ice Accretion was added to the handbook about a year ago.

@Jimmy Great find! I've added that to my answer


text:
Can TAS at different altitudes be calculated if only one performance point is given?
If the POH only gives TAS at only one altitude, can we calculate the TAS at other altitudes?
Here is a snippet from the POH of Remos GX. If we set the RPM to 5,200 then at 3,000 feet MSL ISA we get 107 knots. Can we calculate the TAS at 6,000 feet?

No, you can't. You sit on a quadratic function (actually, a sum of several) and don't know how far you are from the optimum, so you don't know the local gradient (which changes all the time as you move up or down the curve, of course).

If you keep 5,200 rpm at 6,000’, the engine will be producing slightly less power due to density altitude. There will also be slightly less drag so the speed will only drop about 1-2 knots. Because the engine is producing less power, fuel consumption will be slightly less and range will also increase.
The performance figures for a Cessna 150 can give you an approximation of how the numbers change with altitude.

This is helpful in practice. In theory, I guess I can't make any inference about TAS at different altitudes since only one performance point is given.


text:
How to use airport panel information on sectional chart?
In the Chart Supplement, the airport information includes the chart on which the airport is located. It also includes a panel on the chart where the airport is located. How can I use this panel information? Sectional charts don't appear to have panels.
Here is the airport information for San Francisco International:

I understand that San Francisco stands for San Francisco Sectional Chart and H-3B and L-2F are for the IFR charts, but how can I use the 3B and A information?

Unfortunately, there is nothing in the front matter that would explain what those mean.  I do know from that document "A" indicates that airport is on an area chart.  The others appear to be a helicopter chart of TAC chart.  I do not know.

This is a partial answer. I have not succeeded so far in finding an answer regarding the "3B". However, the "A" is addressed in the Chart Supplement.
According to the front matter in the Chart Supplement, the "A" indicates that the airport is depicted on an Area Enroute Chart, in this case on the SFO Area chart.
See the following quote from the Chart Supplement's Airport/Facility Directory Legend:

Charts refer to the Sectional Chart and Low and High Altitude Enroute Chart and panel on which the airport or facility is depicted. Pacific Enroute Chart will be indicated by P. Area Enroute Charts will be indicated by A. Helicopter Chart depictions will be indicated as COPTER. IFR Gulf of Mexico West and IFR Gulf of Mexico Central will be referenced as GOMW and GOMC.


text:
When flying into an area with colder air, how will the altimeter read compared to true altitude?
When flying into an area with colder air, how will the altimeter read compared to true altitude?
Air expands as the temperature increases and it compresses when the temperature decreases, shall I expect it is flying to a higher pressure area ?

There are lots of questions on the FAA Knowledge Tests about altimeter readings at non-standard temperature and pressure settings. The non-standard pressure questions are fairly intuitive. We all know that pressure decreases as altitude increases. Therefore, if the pressure is lower than what the altimeter expects, the altimeter is fooled into thinking it is higher than it actually is. Likewise, if the pressure is higher than standard, the altimeter reads lower than it should.
Dramatic and dangerous effects most commonly occur when crossing a frontal boundary from an area of high pressure to an area of low pressure. If the altimeter is set to the local altimeter setting in the area of high pressure and the aircraft flies to an area of low pressure, without changing the altimeter setting, the altimeter reading will be too high, possibly by hundreds of feet. Less dramatic changes happen all the time when you fly. As an example, right now the altimeter setting at KSBP is 30.08. The setting at KSBA (62 nm away) is 30.01. If you fly to KSBA you would notice a change in altitude of -70 feet when you get the new altimeter setting from approach control. The aircraft is 70 feet lower than you thought. That is the origin of the memory aid, “HIGH TO LOW LOOK OUT BELOW”.
AIM 7−2−3. Altimeter Errors

b. Once in flight, it is very important to obtain frequently current
  altimeter settings en route. If you do not reset your altimeter when
  flying from an area of high pressure into an area of low pressure,
  your aircraft will be closer to the surface than your altimeter
  indicates. An inch error in the altimeter setting equals 1,000 feet of
  altitude. To quote an old saying: “GOING FROM A HIGH TO A LOW, LOOK
  OUT BELOW.”

Instrument Procedures Handbook

When cruising below 18,000 feet MSL, the altimeter must be adjusted to
  the current setting, as reported by a station within 100 NM of your
  position. In areas where weather-reporting stations are more than 100
  NM from the route, the altimeter setting of a station that is closest
  may be used.

You will notice that, when using flight following or flying IFR, after checking in with a new controller, the controller will usually respond to your check-in with the altimeter setting he is using for flights in your area.
Non-standard Temperature
The same thing happens with temperature changes but it is less intuitive because we don’t have day-to-day experience with changing the altimeter with variations in temperature. We also learned about combustion in the engine and associate high temperatures with high pressures and that can lead to us getting tangled up in our thought process. Lets start from scratch and build a mental model of how the altimeter works.
Think of the aircraft as siting in a column of air. The altimeter measures the weight of the air above the aircraft. It doesn’t really know how much air is below it or how high it is above the ground. It just knows that at a certain pressure from the air above it makes it read a specified height. It has been calibrated for standard temperature and pressure lapse rates. If the temperature or pressure don’t change as expected, the weight of the air above it will not be the same as it is calibrated for, and it will give erroneous readings.
Let’s start our thought experiment with temperature and pressure at standard (29.92″ and 15°C) and the aircraft at 5,000′ MSL and AGL. Now imagine that the entire air mass being heated to be warmer than standard temperature. We know from high school physics that air expands as the temperature goes up. The entire column of air now expands and as the column of air expands, the aircraft moves higher in the column. Note that the weight of the air above the aircraft hasn’t changed, it just takes up more room. Since the weight of the air hasn’t changed, the altimeter reading hasn’t changed. The aircraft is now at a higher AGL than it was before but the altimeter still says 5,000′ MSL.

The reverse occurs when air temperature is lower than standard. As shown on the graphic above, the altimeter will read lower than it should if the air temperature is colder than standard. The same memory aid we used with pressure applies, “HIGH TO LOW LOOK OUT BELOW”.
People often get the impact backwards when they try to relate it to knowledge of engine combustion. In an engine, higher temperatures indicate higher pressures. So they think that if the temperature is higher, then pressure is higher. Normally higher pressure means altimeter reading is lower. The reason higher temperatures equate to higher pressures in an engine cylinder is because of the ideal gas law PV= nRT. For a fixed volume, higher temperature means higher pressure. But the volume is not fixed in the atmosphere, so the reasoning doesn’t translate directly to this problem.
For those who care, the standard corrections for temperature are: For each 10° C the OAT is warmer than ISA increase the indicated altitude by 4% to give true altitude. For each 10° C the OAT is cooler than ISA decrease the indicated altitude by 4%.

For temperature or pressure, remember: High to low, look out below.  Low to high, hello sky.
If you maintain a constant altitude indication and move to an area of lower temperature or pressure, your actual altitude will be lower than indicated.  The reverse applies if you move to an area of higher pressure or temperature, you will be higher than indicated.

I think I am not clear to a basic concept...so here..when I flying towards a lower pressure or low temp area, the altimeter overreads...but...for low temp air, the air should be compressed, so shouldn't the air pressure be higher ?

@PJerk  That may be true if the air was being physically compressed, but it isn't.  When it cools pressure (and volume) will decrease.  If you fill a balloon with air and then place it in the freezer, the internal pressure will begin to drop and it will shrink in size because the outside air compresses it to a point where the internal pressure is equal to the outside pressure. In the open atmosphere there isn't that 'outside' pressure, so you just see the pressure drop as the temperature drops.

What about when it comes to the atmosphere, high temperature area —> low pressure ?

@PJerk  temperature and pressure effects are independent.  You have to evaluate each as they vary from the ISA standard atmosphere.  It's not uncommon when flying from one area to another that the temperature and pressure change in opposite directions. JScarry's answer provides more detail.


text:
what is a flap hinge moment?

I am a bit confused on how to come up with the flap hinge moment, like, what force is involved and where is the center that the force is wrt.
And why is the moment as shown in the above diagram seems to be in a different direction from that shown in the diagram below

( video is at

)

You have to think that your flap is a small wing by it's own. The fixation point of this wing, through which all loads must be transferred is at the leading edge. Then there is a moment created at this hinge by both the aerodynamic lift and the aerodynamic moment if your profile is not symmetrical. You can calculate this moment by calculating the lift $L_f$ and aerodynamic moment $M_{0_f}$ at the aerodynamic center and then adding them after multiplying the lift by it's lever arm which is one quarter of the flap chord $c_f$. For a unit length of flap you get the following :
$$ M_h = L_{f}*\frac{1}{4}c_{f} + M_{0_{f}} =\frac{1}{2} \rho c_{f} C_L{_\alpha} (\alpha +\delta) V_\infty^2 * \frac{1}{4}c_{f} + \frac{1}{2} \rho c_{f} C_{m_0}V_\infty^2 $$
For the second part of your answer, the first diagram is showing the moment exerted on the flap to keep it down while the second one is showing the moment applied by the flap on the wing. Newton's third law gives you everything else.


text:
Can a controller be tasked to provide more than one ATC service at a time?
During a visit to one of the ATC Facility  I found out that the Aerodrome Controller was also providing procedural approach control service along with aerodrome control service.
Similarly, Area Radar Controller of the same facility was also permitted to assume the responsibility of Procedural (Non Radar) controller (who acts as a backup to the Radar Controller) in the absence of Non Radar controller to provide relief to him.
I find both of these arrangements a violation of safety. I tried to find some reference to support my idea about this in the ICAO DOC 9426 (ATS Planing Manual) and Human factors Training in ATM, but could not find out anything that specifically prevents or allows this particular arrangement.
Can these services be combined? Any reference to the ICAO doc or some regulation would be a great help.

There are established procedures for combining positions during light workloads. At my field ground/clearance delivery and tower are frequently the same person during slow times. Likewise, when flying cross-country I might have 10 different controllers on a weekday flight into the LA area, but only four or five on a Sunday morning or late evening. It’s perfectly normal and not a safety risk.

I find both of these arrangements a violation of safety.  Please describe your qualifications and credentials to make such a determination.

"I find both of these arrangements a violation of safety" On the contrary, controllers generally make more mistakes during quiet periods with very little traffic, so combining sectors to keep us moderately busy will actually increase safety, from a human factors perspective.

JScarry is right.  Workload dependent, its completely acceptable for an ATC employee to provide multiple services.  No need to have 1 on Clearance, 1 on Ground, and 1 on Tower if you service 5 aircraft an hour.


text:
Is the ATC of the lower and upper areas of the Netherlands combined or segregated?
I am simulating the capacity of the Netherlands airspace by using the sector capacity. But I am wondering for different height, the capacity works for both or a single level.
Therefore, I want to know if the controller control lower and the controller control upper area are from same system or not. The question can be paraphrase as, would there be a controller control both flights for two areas simultaneously?
And if possible, are there any documents explain it?
The map below comes from AIS-Netherlands.

Welcome to aviation.stackexchange.com!

Note that the Netherlands is a bit of a special case.
Below FL245, Air Traffic Control is provided by Luchtverkeersleiding Nederland (LNVL, the Dutch Air Traffic Control) and Dutch Mil (Dutch military ATC). Until one year ago, the Dutch military  operated from their dedicated air traffic control centre in Nieuw Milligen. Since January 2018, they are colocated with LVNL at Amsterdam Airport Schiphol and largely use the same systems as LVNL.
On the lower area map (below FL195), all sectors marked as Amsterdam Radar are controlled by LVNL. The  sectors marked as Dutch Mil  are controlled by the military, and despite some of the sectors are still named NW Milligen, they are controlled from the same room as Amsterdam Radar at Schiphol. As you can see on the upper area map, all sectors are marked Amsterdam Radar.
Their systems are partly combined, but military sectors and civil sectors are never combined. So if a lower sector is controlled by Dutch Mil, the upper sector will be controlled by a different controller.
When both the lower and the upper sector are controlled by LVNL, they can be combined during hours of low traffic. In that case there may be a single controlled controlling flights in the lower airspace and in the upper airspace. Combination is possibly also with adjacent sectors.
But wait, that's not all. Note that the map mentions that the Upper Area is between FL195 and FL245. The upper airspace mentioned so far in this answer, has a ceiling of merely 24500 feet.

Above FL245, ATC is provided by EUROCONTROL's Maastricht Upper Area Control (MUAC). They are located in Maastricht, far away from Amsterdam. They use the same radars, but their control system is totally different. Sectors of Amsterdam and Maastricht can thus not be combined.
Within MUAC's airspace, there is horizontal and vertical sector splitting. Especially the Delta sector is a busy one, with lots of transit traffic to/from UK/Atlantic and with climbing/descending traffic from/to London, Frankfurt, Cologne/Bonn, Brussels, Amsterdam and many more airports.

Thank you so much for your clear answer! It really helps a lot!

Is the Netherlands a special case because just about all of it is a shaded area? Or am I confusing things?

@Mast that too, and with the rising sea level the shaded area may only get bigger :-) It's a special case because there are two air traffic control agencies dealing with en-route civil aviation, each with their own ATC system. The split at FL245 between LVNL and EUROCONTROL is rare. (Belgium, Luxembourg and part of Germany have the same split because of the EUROCONTROL Maastricht centre)


text:
How do pilots detect fuel contamination in flight?
According to the Aviation Herald, an Alitalia Airbus A330-200 diverted en route "reporting fuel contamination".  How can the pilots detect fuel contamination in flight?

the engine stops working :-)

More seriously, there's some useful discussion in the comments of the page  you linked (makes a change, I know). Some combinations of ECAM problems are listed in the QRH as indicating fuel contamination.

F-35s have a method for detecting fuel contamination.  It's linked to their oxygen masks ;-)

If fuel contamination is suspected (because of engine control system fault indications, slow engine responses or rapid engine pressure ratio (EPR) fluctuations), there is an associated checklist procedure to followed which can confirm the contamination:
Fuel contamination checklist as posted by "330 skipper" at Nov 24th 2017 13:47Z on Avherald:

If ENG 1(2) CTL SYS FAULT alert triggered associated with AVOID RAPID THR CHANGES or ENG 1(2) SLOW RESPONSE, and with rapid and
  continuous EPR fluctuation indications on both engines:
  A/THR.........................................................................................................OFF
If EPR fluctuations stop on both engines: ECAM PROC..........................................................................................APPLY
  A/THR.........................................................................................KEEP
  OFF
If EPR fluctuations continue on both engines: FUEL CONTAMINATION CONFIRMED Apply condition: If fuel contamination confirmed
If ENG 1 CTL SYS FAULT and ENG 2 CTL SYS FAULT alerts triggered with AVOID RAPID THR CHANGES or ENG 1(2) SLOW RESPONSE:
  A/THR.....................................................................................................OFF
  FUEL CONTAMINATION CONFIRMED Apply condition: If fuel contamination
  confirmed
If fuel contamination confirmed: LAND ASAP

In addition, the Flight Crew Operating Manual (FCOM) has the following procedure to be followed if fuel contamination is confirmed:

Special thanks to @mins for providing the images of the procedure and the FCOM

On all larger aircraft, I think there are also magnetic detectors in the fuel lines that detect fuel contaminated by extraneous bits of metal that appear, leading to a message in the cockpit. The more common issue is a fuel imbalance warning where duplicate detectors report different fuel loads, and there are procedures and checlists for managing this situation.


text:
Can I fly for commercial jobs with just my temporary certificate?
I just received my temporary certificate and when I called the airman registry to ask how long it would be before I received my permanent copy, they basically told me it was going to take awhile. So my question is, what can I do with the temporary? Are commercial jobs allowed? Can I apply at private companies to fly for them?

What certificate are we talking about here?

If you have a temporary commercial cert and someone will hire you, yes, you can. What makes you think that you can't?  Assuming USA/FAA.

A temporary certificate has all the privileges as the permanent one.

A temporary certificate is valid for everything that a permanent one is valid for; it's just, well, temporary.
14 CFR 61.3:

No person may serve as a required pilot flight crewmember of a civil
  aircraft of the United States, unless that person:
(1) Has in the person's physical possession or readily accessible in
  the aircraft when exercising the privileges of that pilot certificate
  or authorization—
[...]
(iii) A temporary certificate issued under §61.17;

61.17:

A temporary pilot, flight instructor, or ground instructor certificate
  or rating is issued for up to 120 days, at which time a permanent
  certificate will be issued to a person whom the Administrator finds
  qualified under this part.

(See this question for what happens when the 120 days are up.)
As far as the FAA is concerned, your temporary certificate is no different from a permanent one. I suppose it's possible that an employer might decline to hire you until you get a permanent certificate but I think that's highly unlikely within the US (employers abroad might be a different story). I've seen people pass a CFI checkride and start instructing within a few days, for example.

A temporary certificate has the same privileges as the permanent certificate. A temporary certificate expires after 120 days.
If you temporary certificate is about to expire, you can have a new one issued on the spot at an FAA FSDO, with an appointment.  If the FSDO is not convenient, there is a way to request an extension online.
Temporary certificates are commonplace, as any pilot adding a rating will receive a temporary certificate.
Most permanent certificates have no expiration date, but common exceptions are CFI and Remote Pilot certificates.


text:
Has anyone used a 1/4" Y adapter and 3.5mm-to-1/4" converter to pipe in music into their aviation headset?
I have a standard aviation headset and would like to splice in some music for longer flights.  The aviation-specific adapters are overpriced at around $40.  Can i just use a 1/4" Y adapter and a 3.5mm to 1/4" converter, such as these?   Has anyone tried this with results?
https://www.sweetwater.com/store/detail/YPP118
https://www.sweetwater.com/store/detail/CMS103

I'm voting to close this question as off-topic because it's about electronics, not particularly for aviation (and doesn't need to modify the airplane or the headset).

The Y adapters are to split outgoing signals, not combine incoming ones. The other problem is that they don't mute on an incoming transmission. If you want to listen to music as you fly, please buy a headset designed for it so you don't miss important communications.

Also, chances are that the output of your music player is set up for the impedance of a regular audio headset, about 25 ohms, while your aviation headset is likely around 150 ohms.

@mins could it not be that it is better to ask about an aviation device here rather than elsewhere, where aviators may not be very present?

@Abdullah: "could it not be that it is better to ask about an aviation device here rather than elsewhere" Not my opinion at the time (but this is a vote process, the message appears automatically.) I wasn't followed but I think I was right, it took more than two years to get an answer, and neither the question not the answer have any upvote, meaning nobody is interested, not even you. So asking in the appropriate site would have been better.

I’m voting to close this question because it's about electronics, not particularly for aviation (and doesn't need to modify the airplane or the headset).

Commercial 1/4 Jack audio headsets are stereo, signals to top and ring, body is ground... so you need to fiddle the wires so both signals go to the tip... Else you will.only hear one channel .. I don't advocate this use because if you are listening to.music you might miss calls about other traffic etc.. Your call.


text:
How does the throttle position affect the speed of airflow to the engine?
It is said that the less we open the throttle the slower is the speed in Venturi tube, thus less reduction in pressure and less fuel is being sucked from float chamber, however, actually if we reduce the area of the tube by closing throttle ,according to Bernoulli theorem, the speed of air in the same tube should increase, shouldn't it?

That's because it's not the restriction created by the throttle plate itself, that you see as manifold pressure (or vacuum), that is creating the suction that pulls fuel from the carburetor float bowl.  It's the restriction of the venturi, where the main discharge nozzle is, which is upstream of the throttle plate.  Since it's in in the upstream flow, the suction created at the venturi, being a fixed cross section, is a function of air velocity entering the carburetor, which is a function of throttle opening and engine speed.
In other words, the fuel metering system at the venturi doesn't care about the pressure differential created by the throttle plate farther down, it only cares about the velocity of the total mass flow that engine is able to pull past the venturi upstream of the throttle.
Open the throttle, the velocity of the air going through the venturi goes up, the suction generated by the venturi increases, and more fuel is pulled into the discharge nozzle.  And vice versa.

Important to note the SOURCE of the vacuum is towards the top of the diagram above the throttle plate where the pistons are pulling fuel/air into  the cylinders through the intake manifold.  When the throttle plate is more closed, vacuum in fuel spray area is less, and less fuel/air mixture gets into the engine.  Computer controlled fuel injection has replaced this design in cars.  However, it is entirely mechanical and reliable in the absence of icing.


text:
Why commercial planes fly at high altitudes?
L= Clq(TAS)^2*S/2
D= Dlq(TAS)^2*S/2
Some say it is due to lower friction drag due to lower density. However if our weight does not change, that means lift does not change as well. So when air density decreases with increasing altitude, TAS increases to maintan required lift force, thus dynamic pressure remains constant. This leads to the fact that drag must not change as well (keeping in mind that Dl and S are constant). What do i miss?

Lets say you wanted to go somewhere at 700 knots, it would take a lot more fuel to fly that 700 knots at 10,000 feet than it would at 35,000 feet. Yes, drag matches thrust in both situations but it would be a lot more drag and a lot more thrust (and fuel) at the lower altitude. Hopefully somebody can put numbers and explain how your equation works with that.

See https://aviation.stackexchange.com/questions/24641/what-is-the-relation-between-an-airplanes-altitude-and-the-drag-it-is-experienc?rq=1

Because while the dynamic pressures of air reacting on the wings at those altitudes remains the same, the speed of the relative winds, and, as a consequence the aircraft’s ground speed is much higher at higher altitudes than near sea level.  This is as a consequence of the air density being much lower at high altitudes than down low.  Cold thin air facilitates true airspeeds 100-300 knots higher than indicated airspeed does.  Therefore per unit of fuel consumed to overcome drag, the airplane travels much farther and consumes less fuel over the course of the flight.
Example:  jet airplane flying at a pressure altitude of 37,000 ft, Outside ambient temperature is -47°C.  If the calibrated airspeed the pilot reads in the cockpit is 300 KCAS, the true airspeed is 575 KTAS.
Add to this that these altitudes do allow the aircraft to access the upper level winds of the jet stream, which range between 30 to over 160 knots on certain days, which can facilitate a healthy tailwind for eastbound flights around the globe.  It is not uncommon for commercial aircraft to log over 650 knots groundspeed in these conditions, further reducing fuel consumption.
As the speed of sound varies proportionally with temperature, compressibility limitations prevent this form being used beyond Mach .8 - Mach .9 due to Cp movement and control buffeting, depending on the aircraft.    There also is a point in the flight envelop where the Stall speed Vs corresponds with the maximum Mach number - see “Coffin Corner” for further details - so this limits the maximum operating altitude based upon outside air temperature as well.  Nonetheless, high subsonic air travel remains one of the most efficient means of moving large numbers of people and cargo quickly around the globe.

Just to add. Engines also benefit from very low temperatures at high altitudes. https://aviation.stackexchange.com/questions/1609/why-do-jet-engines-get-better-fuel-efficiency-at-high-altitudes


text:
What would happen if the elevators were set to opposite angles?
For example left elevator angle = +30 deg, right elevator angle = -30 deg. Would these settings be able to induce a rolling moment on the aircraft? What would happen with the pitch?

This would be an elevon application (ailerons + elevator).  Found on flying wings and deltas.  Theoretically possible on a standard tail.
With elevons, one up and one down will roll the aircraft with out pitching it.  Interesting that this can be done from the front, back, or center of the aircraft.
Someone may wish to correct me, I believe Burt Rutan put both elevator and aileron function in the canard of one of his planes to simplify the control linkages.
So, as a designer, yes this is possible.

To supplement Robert's answer, this arrangement is used not only on flying wings, where it is indeed ubiquitous, but on many more 'classical' designs.
On flying wings these surfaces are called 'elevons', but in other cases they would be termed 'differential stabiliser'.
Primarily they are found on supersonic swing wing fighter aircraft: F-14, Tornado, MiG-23, -27. The latter, for example, has flaps occupying all its trailing edge, and entirely relies on differential stabilisers and spoilers for roll control. But even non-swing-wing designs (e.g. MiG-25, Su-27) use differential stabilisers to augment roll control (sometimes only in some flight regimes).
Like with any combined control (for example, V-tail), if you use one channel (say, roll), you reduce capacity in the other. This has to be accounted for in the design, typically with increased deflection range and/or surfaces area. But there is no particular difficulty with zeroing the effect in the opposite channel: that is, in most cases deflecting symmetrically ±10° (30 is perhaps too much) will produce roll but no pitch.


text:
Why overhead bin was put on top of passengers head?
Hello I'm just curious about the reason to why the overhead bin was most commonly being put on top of our seat and head.

where else then?

Well, why it's not below the sit? I mean, if the plane fall wouldn't it lower the risk of someone get hit with heavy stuff on their head??

@HermesDjohar You can't put it under the seat, it would raise the seats up about 18-24", then you wouldn't have enough width left in the cabin for the seating arrangement. The seats have to be placed at the widest spot.

I just wondering if the overhead bin can be removed. We can create escape system like jet fighter pilots in the event of plane fall.

@HermesDjohar You want to spend an 8 hour flight strapped tight into a seat and wearing an oxygen mask, for the minuscule chance that you have to eject?

For information about passengers escaping from a falling plane, we have many well-written answers here, here, here and here.

You might also want to see this answer in particular to the question If a pilot ejects, what is the autopilot programmed to do?

Also note that in a jetliner, there is literally tons of stuff above the passenger compartment. You really don't want to shoot through that at 20 g.

Well, if you put them under the seats they wouldn't be overhead bins anymore.

@Jules Of course, then the question is: why don't airlines install underfoot bins?

... but you can stow your bag under the seat in front of you.  Always have been able to.  No need for a lower bin.

Because it is the most efficient use of space.
Due to the physics, specifically the way pressure differential is spread in a container as stress, a perfectly circular tube is the best shape for the body of an airplane, and a rectangular box is way, way, worse. Modern airlines have an oval cross-section, but it is still a lot closer to a tube than a box.
The question is than how do you allocate the space inside a tube. The widest floor area is in the middle vertically, so that is where the passengers go. Now we have roughly one to two meters of vertical space both above and below the passenger deck, not high enough to accommodate people but enough for cargo and storage.
Naturally you would want the heavy cargo to go below, and passenger storage to go above, for logistic reasons. Putting them on the same deck as the cabin would reduce the usable floor area for putting seats. You'd want maximum floor area to place the maximum number of passenger seats to increased revenue on the same flight.

Not a bad question.  First sentence sums it up perfectly.

The Soviet Ilyushin Il-86 briefly tried the "luggage at hand" idea, where passengers loaded their own luggage on a lower deck as they boarded (similar idea to some trains with passenger loaded baggage racks at the end of carriages). The twin aisle Il-86 only had overhead bins for the window seats,

People need to store their carry-on luggage somewhere. The space above passengers' heads is usable space. So it's only logical to store carry-on luggage in the space above passengers' heads.
You ask:

Well, why it's not below the sit? I mean, if the plane fall wouldn't it lower the risk of someone get hit with heavy stuff on their head??

Cargo is already stored underneath the seats. Checked baggage is stored in the cargo hold underneath the passenger compartment. Small carry-on items can already be stowed directly underneath the seats. There's no additional room for baggage underneath the seats.
Removing the overhead compartments would reduce the risk of someone getting hit in the head by falling baggage, but as far as I know, these injuries are already rare.
You also write:

I just wondering if the overhead bin can be removed. We can create escape system like jet fighter pilots in the event of plane fall.

No, it's not feasible to create a fighter-style escape system. See: Could ejector seats save lives in commercial aircraft?

"People need to store their carry-on luggage somewhere."  Why can't people just check it, like they used to do?  Who is in such a freaking hurry that they can't walk down to the baggage carousel and pick up a bag carrying a weeks worth of stuff (based on the size of things I see stuffed into overhead bins) when it comes out?

@CrossRoads Well, some items are allowed in carry-on luggage but not checked luggage. Some items are things that the passenger would like to use during the flight. Checked luggage is more easily stolen than carry-on luggage. As you mention, picking up checked luggage takes time. Even if checked luggage didn't have these disadvantages, that's not an argument for removing overhead compartments.

@CrossRoads a lot of airlines now charge for checked baggage but allow carry on for "free" (i.e. included in the initial ticket price). I flew carry-on all around Europe this summer to avoid an extra 15-30€ per bag per flight. It wasn't about the speed, it was about the price.

@CrossRoads: Because sometimes what's in carry-on luggage is stuff you might want during the flight.  For instance a sweater, laptop computer, books to read...

@CrossRoads If I don't need more space, why would I want to get to the airport early, stand in line at a counter, check my bag, walk farther through the airport, find a baggage claim, and wait around for up to 40 minutes? And I risk my luggage being lost, which means that even if I do check a bag, I need to carry on necessities anyway, including toiletries, electronics, and a change of clothes in case my bag is lost (failing to do this is how I once ended up at a fancy New Years Eve dinner in a grubby old t-shirt).

And that's why boarding and deplaning take so long. I hate flying commercial anymore.


text:
confusion between RNAV and RNP approaches and specifiations
Ive been really confused between these two specifications recently. For example my research suggested that RNP has on board monitoring and alerting and RNAV doesn't require this, however then why must we compute a RAIM check before conducting an RNAV app when for RNAV specification no alerting or failure detection is required and hence TSO 129 may be used? Also doing my flying in Australia some ADs would state there is an RNAV app available for one runway and also an RNP, what additional requirements would there be in terms of pilot training or alerting etc for the RNP app. Appreciate all answers just trying to get a grip with this confusing concept!

RNAV was/is in the older model where each approach was designed around a specific technology, and any detected failure to meet the (assumed) fixed accuracy of that technology means you can't use the approach at all.
RNP is newer ICAO terminology under their Performance Based Navigation model, which essentially means they don't care how you get your navigation data, just how accurate it is.  The better your Actual Navigation Performance is (i.e. lower number), the lower the approach minimums you get to use.
TSO C129/C196 systems cannot be used as the sole navigation equipment because it only has fault detection, not fault exclusion; if the RAIM detects a fault, you have to stop using it and switch to something else.  (If you don't have RAIM, you have to actively cross-check the GPS, so you might as well just use the other system as primary.)  Notice the parallels to the explanation of RNAV above.
TSO C145/C146 do have fault exclusion, so they can be used as the sole means.  They also support SBAS (aka WAAS), which can offer much lower approach minima where available, but they will gracefully degrade to higher minima depending on the signal accuracy--which can vary over both space and time for the same equipment.  Notice the parallels to the explanation of RNP above.


text:
How does a helicopter hover?
Technically, unless a helicopter's centre of gravity and centre of lift (centre of the rotor) are in perfect alignment, it would generate a pitching moment which would make it unstable.
So, how does a helicopter manage to solve this issue. (I'm assuming it's impossible to perfectly align the CG and the centre of lift due to practical loading conditions.)

It is unstable, the pilot hovers by constantly adjusting controls.

Helicopters can't fly, they're just so ugly the Earth repels them ;)

functional description of a helicopter: an oil leak, looking for a place to crash.

The truth is, nobody knows. Some say it's God, others say it's the pilot's ego keeping the helicopter afloat. I personally think it's a little of both.
Seriously though it's extremely unstable, you are constantly making tiny adjustments every few miliseconds to account for every tiny variable. Go try it sometime, it'll cost at most $500 for an intro flight, and that's if you're too fat for the R-22 like me :D

A helicopter can hover without the CoG being directly underneath the rotor hub, because the rotor hub can apply hinge moments:

Fully articulated hubs with a hinge offset and fixed hubs apply direct mechanical moments to the fuselage, which line them up with the rotor angle.

The rotating blades are subject to centrifugal forces, which pull the rotor hub in the plane of the rotor deflection. As soon as the rotor plane changes as a result of cyclic stick input, the resulting rotor hinge moment will change fuselage angle accordingly, providing the desired feedback cue.
Any helicopter, regardless of the type of rotor hub, has an aerodynamic coupling between fuselage attitude and rotor attitude. A teetering rotor such as on Bell 212 and R-22 does not produce above mechanical rotor hinge moment. In flight, a helicopter is suspended from its rotor, with the Centre of Gravity underneath the centre of lift, unless the rotor can apply a hinge moment to the fuselage. With a rearward CoG and no hinge offset, the following could happen:

The helicopter has taken off vertically, nose tipped up first, and cyclic forward was input. If the rotor had a hinge offset the fuselage would tilt forward, but with a teetering hinge like in the question there is no centrifugal force acting on the hub, and fuselage position now depends only on CoG location. The upward nose angle has consumed some of the useful forward tilt of the cyclic stick. Visibility is impeded. Fuselage tilt provides no direct feedback of the cyclic position.

Fortunately there is an aerodynamic rotor hinge moment, created by the aerodynamics of flapping. The picture is from Helicopter Performance, Stability and Control by Raymond Prouty. It shows that at first, the rotor acts as a gyroscope and stays in its plane. But the blade feathering is referenced to the shaft, and angle of attack of the right hand blade is increased, left hand blade decreased. The rotor will then flap until it is perpendicular to the shaft. With teetering rotors, there is an indirect aerodynamic coupling between fuselage and rotor shaft: the fuselage attitude still follows the rotor attitude but at a slower rate.

The CoG cannot be placed anywhere, it must remain in the area where the moment caused by gravity pulling on the CoG is lower than the maximum hinge moment. But with all helicopters, there is a region of useful CoG.

You should link to your previous answer that you took a lot of this information from since it can provide context (for example, why you talk about a teetering hinge).

@RonBeyer The teetering hinge and the articulated hinge are both mentioned in this answer: one would think that the teetering hinge behaves like OP states, but it does not. The other question was a different one (does the fuselage follow the rotor). There was a lot of static on the line with that question, a link would be more confusing than enlightening in my opinion.

If the center of lift is above the center of mass then the craft will rotate until the center of mass will be directly below the center of thrust. After that the rotation will come to a stop. If dampened the pendulum action will stop eventually
The rotor blades of a helicopter change their lift depending on where they are in the rotation and the position of the cyclic. This allows for precise control of the center of lift by the pilot which in turn will control pitch and roll the craft.
In hover the rotor will be horizontal and produce very little to no horizontal thrust.

"If the center of lift is above the center of mass then the craft will rotate until the center of mass will be directly below the center of thrust." - Are you sure about that? Do you have a source? That sounds similar to the pendulum rocket fallacy. Also, do you have a definition of "center of thrust" which defines it as a specific point?

@TerranSwett Since the is a hinge between the blades (which produce lift) and the helicopter fuselage (which includes the cg), a pendulum effect is indeed possible and active in helicopters. However, cyclic control and a stiff rotor shaft mask this somewhat.


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How does the V22 Osprey manage such high rotor speeds without shock waves?
I read somewhere that the engineers presented an ingenious solution to the rotor tip shockwave problem, except the article didn't actually explicitly mention it.
So, does anybody actually know if such a solution even exists ? And if yes, what is it ?

The Osprey's engines drive the rotors at 412 RPM in heli mode or 333 RPM in forward-flight mode, according to this article. With a rotor radius of 5.8m, that puts the tip velocity at 250m/s, or about 75% the speed of sound, at the higher RPM. So they aren't near supersonic yet because the blades are short enough.
But there is a possibility of reducing blade length for higher forward speed and RPM, and there is research into how to make that possible on-the-fly:

Helicopter performance depends on the length of the rotor blades. For heavy lifting, a large rotor works best, but short blades reduce drag and ultimately allow for higher maximum speeds. Farhan Gandhi, a Penn State University professor of aerospace engineering, has devised an elegant, simple way to achieve both configurations in the same aircraft, using the same rotor.


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What is this biplane?

What is this biplane shown above?

Welcome to Avaiation.SE! You seem to have a grip of how this site work, though if you haven't already done so, could I suggest reading the [help] and maybe take the tour. To improve your question, could you provide some context on where you found/saw this image?

Blackburn T.5 Ripon

The Blackburn T.5 Ripon was a British carrier-based torpedo bomber and reconnaissance biplane which first flew in 1926. It was used by the Fleet Air Arm as a torpedo bomber from 1930 until 1935. Ripons were also sold to Finland, where they continued to be used in action in the Winter War and the Continuation War until 1944.

(Source: iwm.org.uk) The exact one, number 4 on the side.

A Blackburn Ripon Mk.IIA torpedo bomber of No 811 Squadron touches down on the flight deck of the fleet aircraft carrier HMS FURIOUS.

I assume the number 4 just means it is the fourth aircraft in that squadron.  I believe the Baffin aircraft superseded the Ripon so it could even be the same squadron.

Thank you Mike for the information. It is a photograph that I have found in my father in law who passed on in 2009. My wife tells me his older brother was in the RAF  but this is a photo from a local company in Bognor where they lived .The photo is not very clear but I noticed the number behind the large 4 ends in 74. Unfortunately the wing strut gets in the way . Nevertheless it is fascinating reading about this plane and what role they had to play mid wars.. Again many thanks for your help. I use to go to Biggin Hill air shows when I was a lad and still see a Spitfire down at Bognor W Sussex


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What does CSTR means on an Airbus FCU and what happens when CSTR PB is pressed?
I am searching for:

The use of CSTR PB on Airbus FCU &
During what phase is it used?

Thanks

It's a Constraints button that When pressed shows altitude or speed constraints at a certain waypoint.
It would normally be used on departure or arrival from or into an airport when there are many constraints that need to be met.


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What is the material and font used on the panels of most cockpits?
I am working on a project for one of my aerospace engineering classes and was curious to see if anyone knew what type of material is used to make the panels of a cockpit (preferably a 737) as well as the font used for the lettering?

Materials: You'll find several materials used for visible 737 flight-deck panels and structure. Most of the panels themselves are aluminum plates, with fiberglass, kevlar, and other plastics rounding out the space.
Font:  Boeing uses something close to a flavor of Futura on its panels.


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Other than a handful of airlines, do any small operators take PPLs and pay to train them to commercial?
Are there operators out there who take SEL private pilots and train them to commercial?  Do small operators like banner tow, agriculture, skydiving do that at all?  Is it way too presumptuous to ask?  To specify, I'm particularly interested in the US, especially California.

Like a Catch-22, isn't it? Need to have a Commercial rating to be able to be paid to fly, but as a private pilot you can't be paid for your time yet.

You can fly for free as a safety pilot for people working on their instrument rating. The hours count toward your instrument and commercial rating. Check with the local flight schools and ask around to see if any instrument pilots need someone to sit in the right seat while they keep current. I probably have 40 or 50 hours in the right seat, just because I like flying for free—not to build hours.

With the airlines that do offer such programs, the cost is offset by having a pool of new pilots who they can train to their liking from the start rather than having to retrain existing pilots. They also tend to be large operations for whom the cost of having some trainees on staff isn't a major factor.
For a small operator it's typically too expensive to carry the burden of your training cost as well as employing you while you can't fly commercially (which you won't be able to unless you've completed that training.
So unless they have an opening for a non-flying job you can do, with training provided as part of your payment for that job, they won't be able to employ you.
As most jobs tend to require training and certification that involve aircraft, such a job would almost certainly be something like a desk job, answering phones, cleaning, stuff like that, not something someone interested in a flying job is likely to greatly enjoy, increasing the risk to the company that the candidate is going to quit on them.

The only way that would work is to hire on in a non-flying job for a flying school that has an aircraft you can fly as a PPL and fly it around and get training in lieu of pay.


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Does the Lilium VTOL wings produces lift during takeoff?
I just had a look on some of the recent development in the personal VTOL electrical aircrafts.
I am wondering if the Lilium VTOL wings produces lift during takeoff?
I would expect a quit high wind speed moving over the wing generating negative pressure, hence, beside the thrust force generated by the fans additional lift is generated over the wings? Is this correct?

The Lilium seems to have a bank of mini - thrusters encased in flaps. the flaps are angled straight down on takeoff - how would there be windspeed over the wings? The part of the intake air coming from the front? Why would that be 'high speed', seeing as the air can also reach the intake from every other direction?

@bukwyrm you are expecting that there will be no high speed flow over the wings?

If the thrusters point straight down, the inlet can get airflow from every angle , why would the air above the airfoil be especially moved?

The take off is aided purely from the mini fans which is pointed vertically at the aft of the wing to generate pure vertical thrust. The wings will generate only drag and zero lift because the airflow(aerodynamic force) is attacking perpendicular to the chord line. Hence the wings are used only to aid the flight in cruise.

+1, the "claim to fame" with Lilium is the seamless transition from "all lift from engines" to "all lift from wings" in a simple and robust manner. Or that is at least what their marketing material suggests. Whether it will actually work like that...

We don’t have enough information, but there are electric fans mounted on flaps which are sucking air over the wings  - even when the flaps are vertically placed,  it still should produce some suction (and airflow)  over the wing area, too. This amount is probably small, and in my view, this high lift system be would ideal for STOL configuration – Lillium is a bit secretive, but on the recent photos there is a conventional landing gear – so,  maybe,  they will go for STOL, instead of pure VTOL operation.(https://lilium.com/technology/) But, this configuration – “fans in the flaps” is quite a novelty, most probably this is also the best and most elegant way to get full benefits of blown flaps concept – on blown flaps than “suction flaps” configuration!


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What is the structural impact on the wing if no fuel is stored in the wings and just in the fuselage?
What is the structural impact on the wing if no fuel is stored in the wings and just in the fuselage and how to counter possible advantages/disadvantages? Has this topic already been researched?

Please don't re-post your closed question (now deleted)! Wait for it to be re-opened. And please address the points from Federico's comment first...

Sorry for that. I already adressed his points. What remains unclear?

It is unclear to me what exactly you want to know. "What happens if..." isn't really a specific question (like e.g. "How much thinner could wings be if..."). Right now, it sounds like you want to start a discussion about this topic, but this site is not a discussion forum. Have a look at the tour to learn more.

Thanks for your input. I've modified this question.

Your question implies that planes currently store hydrogen in their wings.  But there are no planes that store hydrogen in their wings (at least that I am aware of), the energy density is way too low.  Planes run on jet fuel, which is basically kerosene.  Jet fuel is stored in the wings.  Are you asking about the impact of not storing jet fuel in the wings?

Exactly this is what I mean

I get the impression you're trying to ask "what if we ditch wet wings and also use hydrogen"

Actually, there have been hydrogen powered aircraft: https://www.cnn.com/travel/article/zeroavia-zero-emission-hydrogen-planes-spc-intl/index.html

But my question is focussing on the impact on wing design...

Related -- https://aviation.stackexchange.com/a/56540/34686 -- specifically the paragraph reading "Similarly, if more of the weight is distributed along the wingspan, the bending stress on the wing spars will be less, for a given total force in pounds generated by the wing. So if the wing spars are the critical component of concern that governs our choice of maneuvering speed, then if we increase weight by adding it to the wing, the maneuvering speed should go up, but if we increase weight by adding it to the fuselage, the maneuvering speed should go down."  Also the preceding paragraph.

We may have some other questions about the advantages of "span-loading" here on ASE, as well –  For example-- https://aviation.stackexchange.com/questions/42613/why-are-fuel-tanks-in-the-wings-filled-first-and-why-are-they-used-last/42614#42614 .

This has been well-studied, here are the basics.
For the case of fuselage tankage for fuel: The structural loads caused by the weight of the fuel in a fuselage tank must be transmitted between the wings and the fuselage. This means beefing up the wing-to-fuselage attachment points, which is not required if the wings carry the tankage instead. Putting the tankage in the fuselage also means less room for passengers and cargo.
The best place for this fuselage tank would be right at the center of gravity so the CG shift with fuel consumption is minimized- which unfortunately puts the tank right where the passengers sit. And because this places fuel in close proximity to passengers, it creates a risk factor during a crash.
There are more subtleties involved, but these are the primary considerations. I invite the experts here to weigh in with more details.

@ymb1 Previous versions of the B-52 also held their fuel in the wing, albeit in rubber bladders. Those added weight, too.

I'm a vibrations guys (although not specifically wing vibration), so let me add one point to complete niels nielsen's answer.
If the mass of the wings is reduced by removing the fuel, but the stiffness of the wings stays the same, then the natural frequencies of the wing will go up. A higher natural frequency would have an effect on flutter margin (probably makes it better). Dynamic loads on the wing (e.g. fan blade out loads) would also be affected, although it would be hard to predict if these would go up or down.  Likely for some components, these loads would go up, but for others they would go down. By components here I am referring to things like the engine mounts, pylon, and pylon to wing connections.
On the other hand, if mass is removed, you could keep the natural frequencies the same by reducing the stiffness a comparable amount. This would save weight and likely cost.
I don't have exact numbers for either case, but it should be an appreciable amount.


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What happens to manifold pressure reading following a reduction in both throttle and RPM?
This was one of the questions in my online ground school quiz (PPL), detail as follows:
To set climb power, you reduce the throttle (manifold pressure) and then the props (RPM lever). After setting the props you expect the manifold pressure to:
A) not change
B) temporarily rises than fall again to where it was
C) fall slightly
D) rise slightly
My original answer was there is no net change in the MP reading after performing those two reduction actions.
My understanding of MP reading is that a reduction in throttle would mean more suction/vacuum as a result so the MP reading would decrease. On the other hand a reduction in RPM would mean less suction/vacuum so the MP reading would increase.
Because of the above, and that there is no other detail from the question as to how much changes each action had, wouldn't it be correct to expect MP reading to first decrease (from the throttle reduction) and then rises back again (from the RPM reduction). The net change therefore should be 0.
The correct answer however was d) slightly rises.
The explanation that was given is because the airplane was transitioning from take off power to climb power.
Why does MP rises slightly in this case?

I think you misread the question. Assuming you quote it properly,

To set climb power, you reduce the throttle (manifold pressure)

… so the first step does reduce the manifold pressure and is therefore not subject of the question …

and then the props (RPM lever). After setting the props you expect the manifold pressure to:

… only the second step is.
In the second step, the manifold pressure slightly increases, which

On the other hand a reduction in RPM would mean less suction/vacuum so the MP reading would increase.

… you already understand.
So yes, the manifold pressure decreases first—when you retard the throttle—and then increases slightly as you reduce pitch. Just the question only targeted the second part.
The increase won't be back to the original value, because the throttle is still partially closed. With wide open throttle the manifold pressure is (for normally aspirated engine) almost ambient pressure and there is nowhere higher it can go.

Ahh yes...I think you are right, I misread the question. I wonder why the portion about setting climb power and reducing throttle is even included if the question was just about RPM and MP reading. Thank you for the additional clarification, my original answer is definitely still wrong in that case, you've helped me understand MP reading more.


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Is rate of turn information (both Turn Coordinator and Turn Indicator) accurate only in balanced turns?
I was studying the difference between the TC and TI, and I thought I heard or read somewhere before that the turn rate information on the TC or TI are only accurate when the ball is in the middle.
Let's say I'm in a left turn and the TC shows I'm on the rate one mark, but the inclinometer is showing a slip (left ball).
A slip means I will need less bank or more rudder to be coordinated.
In this situation am I still getting a rate one turn despite being in an uncoordinated turn? And is there any difference here between the TC and TI?
My guess is the turn rate information is independent from the inclinometer, and so I am still turning at a standard rate but uncoordinated.
Is there any truth to the statement that the turn rate information is only accurate when the ball is in the middle?

See what your turn rate is when taxiing... that's an uncoordinated turn, but with a knowable rate.  I suspect you'll find that turn rate is turn rate, independent of coordination or lack thereof.

I think that's correct for a T&B but for a TC, being sensitive to roll attitude from the gyro being canted, I believe slips and skids throw off the indication a bit.  You'd have to go flying around timing turns with a stopwatch to find out.

Sounds like a great question for some actual in-flight experimentation.  I'd love to see someone go up and try it and report back.  Use the extreme cases of a wings-level turn and a fully coordinated turn.  Use an aircraft that still has the old-fashioned "Steam gauge" instruments.  Have a helper carefully time the time per 360 degrees while you focus on flying as precisely as possible.  Find out whether the theoretical errors noted in my answer are detectable in actual practice.

The physics of turn coordinators, and turn rate indicators, are complex.
The since the gyro axis is not usually not perfectly horizontal, the instrument shows some response to pitch rate, as well as to turn rate.  In a coordinated turn at some particular turn rate, the calibrated markings can only be perfectly accurate at one specific pitch rate.  This means we have to specify either the bank angle or the True airspeed when we calibrate the instrument for a given turn rate.  In practice, the True airspeed is specified and assumed to be constant regardless of turn rate, while the bank angle, naturally, varies with turn rate.
Errors from flying at a different True airspeed than the instrument was calibrated for may be small enough to generally ignore in actual practice, but they do exist.
This is explored in more detail in the following ASE answers to related questions--
May turn rate indicators (and turn coordinators) be calibrated to be accurate at all airspeeds, or only for one?
Are turn rate indicators calibrated to a certain speed? If so, what speed?
In some "turn coordinators", does the gyro spin opposite to the direction it spins in a "turn rate indicator"?
If the aircraft is slipping or skidding, then the relationship between True airspeed, bank angle, pitch rate, and turn rate is altered, so the calibrated markings will no longer be accurate even if the True airspeed is the one that the instrument is calibrated for.  For example, in a wings-level skidding turn, the pitch rate is zero.  For the reasons explored in the above links, this will create some change in the turn rate indication.  The indicated turn rate will be different than if we were flying at the same True airspeed but in a fully coordinated turn.
Another way to look at it is that all turn rate indicators, and some if not at all turn coordinators, are designed so that the gimbal axis of the gyro stays approximately horizontal relative to the earth during any given coordinated turn.  If the aircraft is not banked at all, then any turn will tilt the gimbal axis of the gyro away from horizontal, which will affect the sensed turn rate.
Of course, it could happen that a change in indication due to slipping or skidding could exactly offset a change in indication due to flying at some True airspeed that is different from the True airspeed that our instrument is calibrated for.  So the full answer to the question is "Generally, yes, but it's complicated."
The details discussed in the third link above suggest that there may be fundamental differences in the way that a skid, or a slip, affects the reading of a turn rate indicator versus a turn coordinator--i.e. whether the indicated turn rate is increased or decreased-- and furthermore that there may be differences in behavior between different makes of turn coordinator, because they may not all share the same direction of spin of the gyro wheel.
This would be fertile ground for some actual in-flight experiments to make some real-world observations as to how the turn rate displayed by a given instrument is altered by slipping or skidding.  Keep the airspeed and the indicated turn rate constant, and make the aircraft slip or skid through one or more full 360-degree turns, and measure the actual time to complete 360 degrees of turn in each case.  For completeness, repeat the experiment at a different airspeed, or a different indicated turn rate, or a different amount of deflection of the slip-skid ball.  Be sure to include the extreme case of a wings-level skidding turn.  Finally-- especially if flying with a turn coordinator rather than with a turn rate indicator-- do some basic tests to see if, starting from a standard-rate turn, moving the stick or yoke aft to "pull" some extra G's tends to boost, or to reduce, the indicated turn rate.  Similarly, starting from a standard-rate turn, test whether moving the stick or yoke forward to "unload" the wing to a lower G-load tends to boost, or to reduce, the indicated turn rate.  These tests will help show which direction the gyro wheel is spinning in that particular instrument, which is relevant to understanding what is going on in the slipping or skidding situations.


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Which "Power Available" graph is more correct?

Trying to understand the drag and power required/available graphs for a piston + propeller airplane. Both graphs are from current book/website and while they are showing mostly the same thing, I noticed the shape of the power available curves are different.
If I have to guess I think the second graph make more sense, since power available from a piston engine should be almost the same throughout the entire speed range.
*If the above is true, can you please also explain why it's not a perfect horizontal line across? Ie: if the engine is rated for 150 BHP, then the line should be at 150 BHP, other things equal (density altitude)
I feel like I'm missing something fundamental here but can't seem to work this out.
Thanks

As far as I can see the graphs are the same and could represent the exact same aircraft, the only difference being that the ratio of vertical units to horizontal units has been changed, "stretching" out the upper graph.

Whether or not the graphs are identical certainly would be up to the artists eye, but working through the units and definitions may be helpful.
Most of us know "power" as engine output in "horsepower" but it can also define the energy state of an object that is propelling itself as Power = Force x Velocity with units of kg m/s$^2$ x m/s.
The propelling force is Thrust.
Horsepower carries the same units as: Torque Force x distance/time as engine "power" output, which is proportional to fuel burn/time and equal to prop drag x distance/time.

Which "Power Available" graph is more correct?

They both are if we understand them.  The first one is based on Thrust x Velocity of the aircraft.  Factor out Velocity and you have a perfectly sensible graph with L/D max right at the bottom of the curve.
The second one shows "horsepower available" based on engine RPM, which improves slightly for fixed pitch props that reach optimal AOA and less blade interference at higher airspeeds.  Essentially, the prop allows the engine to run at a higher RPM because it is creating less drag.
"Horsepower required" is how much engine torque is required to turn the prop at a sufficient velocity to create sufficient thrust to match the aircraft drag.
Why they don't just plot thrust vs drag is beyond me, but working through the units and nomenclature seems to help.

Power is work getting done over a period of time.
Work is force multiplied by distance.
So when you are sitting at the beginning of the runway, at full throttle and brakes on, while thrust available is very high, power available is 0, because no “work” is getting done.
Edit- basically you are applying a lot of force, or using a lot of thrust, but since distance traveled is 0, no work was actually done.
Which is why the power available is indeed 0 at a velocity of 0, and increasing rapidly.
Note- the second graph is exactly the same as the first, only it is showing the curve beginning at some point after the stall speed.


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Instrument approach DME VS instrument approch ILS DME
what is the diffrence of Instrument Approach DME and Instrument Approach ILS DME?
Is it same as LOC DME APCH and ILS DME APCH?

The name for each approach indicates what equipment is required, so DME, ILS/DME and LOC/DME would all be different--and some aircraft may be able to fly one but not another.  Generally, the better (i.e. more precise) the equipment available, the lower the minimums can be because the obstacle clearance area will be smaller.


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What steps are airlines taking to retain and acquire pilots?
It's well known that there's a global commercial pilot shortage, likely due to the cost of becoming a pilot, as well as the lackluster starting salaries. I've heard that airlines are making pushes to acquire new pilots, as well as retain current ones, but what steps are they taking to accomplish this?
Please link to sources if you can.

Take a look at what Lufthansa does for pilot training, a similar program is offered by a number of different airlines...

It's not the cost.  Learning to fly has always been an expensive pastime (a new C-172  was the price of a nice house in the 60s) and the difficulty in getting a career started was WAY worse 30 years ago.  The main factor is demographics.  The baby boom wave is hitting retirement age and the pool of potential new pilots is getting smaller and smaller.

@JohnK Learning to fly has always been an expensive pastime, but recently it has become more expensive. The FAA has increased hours requirements, flight requirements, and criteria for credible hours. The aircraft have also gotten more expensive to fly. Plus, new 172's are still the cost of a nice house today (well above the median home price in US).

Well yes what you are talking about is the Colgan rule, which was a fiasco but that only affects the US and its effect is to keep new pilots with the 3rd tier carriers longer until they get to 1500 hrs.  It had a negative effect on Regional airline recruiting in the US. Most other western countries also have a shortage, and it's mostly related to the demographic wave I mentioned.

@JohnK Quite a lot of articles and studies would disagree with you. The demographic issue does effect it, but to say that cost is not a factor is unequivocally false.

These days it's about 50k to get to a Comm with a Group 1 IFR.  That's in much more expensive Canada.  That's about 10k in 1975 in constant dollars.  10k was about what it was going to cost me to get to the same place in 1975, so I stopped at Private until much later.   It WASN'T cheaper in some halcyon old time.  To the extent that training requirements are more compared to long ago, yes there is a difference, but way less than the fact that the potential pilot pool is very small today.  When I came of age in the 70s I had massive competition from all my mid BB wave compatriots.  That's gone.

Standard minimum cost quoted by flight schools is 70k in USD. Costs vary by sources, but in the 60's/70's, it seems to roughly hover around 7-15k USD, and when adjusted by year, still shows a roughly 55% cost increase. On top of that, there were many pilots coming out of the military at that time who had much lower commercial training costs due to their experience, meaning the overall costs were even lower.

There ya go... 50k... http://flaviationacademy.com/become-a-commercial-pilot-1/?gclid=Cj0KCQiA8f_eBRDcARIsAEKwRGe0VaOMbI_dokXjzwchbCyJhD5SJfTowNil7f39OvEZKYlImcvDLNwaAogFEALw_wcB   70k is at one of those comprehensive colleges.

@JohnK That includes 247 hours for your commercial single/multi license. That doesn't involve getting to the 1500 hour mark to be able to fly for an airline.

1500 hours would cost a quarter million! Nobody on a career path pays for that out of pocket.  Nobody.  You get a lower level job and work it up.  Guys were going to the Regionals, in many cases, right from those schools with 250hrs until the Colgan Rule.  Now they have no choice but to take the lower tier job instructing or flying a 1900 or something until they get to 1500.  Fact is though, this is the BEST time ever to be trying to get a flying career going.  Without question.